ES2369593T3 - PROCEDURE TO MARK AN OBJECTIVE THAT SOUNDS SOUND. - Google Patents

Abstract

The invention relates to a method for locating a sound projecting target by means of an elongated underwater antenna (10) having a plurality of electroacoustic converters (11), wherein a horizontal target location (ß<SUB>zk</SUB>) is determined in the water as the target in a directionally selective manner from the receiving signals of the converters (11), including a measured variable (C<SUB>mess</SUB>) of the acoustic velocity. In order to compensate the systematic location error inherent in such an underwater antenna, which may lead to erroneous locations particularly in the case of greater locating angles, the acoustic radiation course is calculated in the acoustic distribution direction specified by the target location (ß<SUB>zk</SUB>) by means of an acoustic distribution model, and a vertical acoustic incident angle (?<SUB>k</SUB>) is determined at the location of the antenna from the acoustic radiation course for an estimated distance and depth of the target. A correction factor is deduced from the vertical acoustic incident angle (Yk), and the measured variable (C<SUB>mess</SUB>) of the acoustic velocity is corrected by multiplying the measured variable by said acoustic incident angle. Locating in turn is carried out using the corrected variable (C<SUB>einstell</SUB>) of the acoustic velocity, and an improved target location (ß<SUB>zk</SUB>) is obtained.

Description

Procedure to mark a target that emits sound

The invention relates to a method for marking a target that emits sound by means of an elongated underwater antenna having a multitude of electroacoustic transducers according to the preamble of claim 1.

In the case of a known marking procedure for the passive location of a target or target that emits sound, that is to say that generates sound, that reflects sound or that disperses sound (EP 01 308 745 B1) an antenna called linear antenna is applied with a multitude of electroacoustic transducers, placed glued to each other. A linear antenna of this type is, for example, called towed arrays or lateral antennas (flank arrays) arranged in the body of the ship. The linear antenna tends a reception sector within which incoming sound that is emitted from the target or the target and propagated in the water is received by the transducers. In order to determine the direction of the incoming sound with the reception signals of the electroacoustic transducers, a fan of the polar diagram or beams covering the reception sector is generated by a so-called address generator or beam generator. Each electronically orientable polar diagram in the horizontal direction with respect to a reference direction has a relatively small horizontal opening angle and a more or less large opening angle depending on the number of electroacoustic transducers arranged vertically, as well as a direction Main with maximum reception sensitivity. The horizontal direction, perpendicular to the submarine antenna, also called perpendicular direction, is usually chosen as the reference direction. For the generation of the different polar diagrams or beams, the reception signals of the transducers are delayed, and specifically in such a way that they are cofasic for the respective pivot angle of the main direction of the polar diagram and the cofasic reception signals are summed to form the so-called group signals that form the polar diagrams. The delay times for the reception signals of the individual transducers are measured by the sound velocity measured at the antenna site, the position of the transducers within the underwater antenna and the angle of rotation of the respective polar diagram. In the case of sound reception in the range of the polar diagram, the polar diagram in which there is a maximum of sound reception is available. This is determined because the maximum level of the group signals that form the polar diagrams is detected. The pivot angle of the main direction of the polar diagram is emitted as target marking. Target marking is represented numerically or graphically on the marker.

In the case of linear antennas of this type with the pivot angle of the main direction of the polar diagram or with the size of the marking angle, both the horizontal opening angle and the vertical opening angle of the polar diagram or of the beams vary . In the case of a perpendicular marking angle of 0 ° with respect to the underwater antenna, the horizontal opening angle is the smallest or the vertical opening angle is the largest. As the marking angles increase with respect to the forward or forward direction of reference, the vertical and horizontal opening angles of the polar diagrams approach each other.

In Figure 1, the contour line 3dB of a polar diagram marking a target or of a beam marking the objective of a linear antenna is drawn as an example in the case of three pivot angles different from its main direction, it is that is, in the case of three different target markings or β marking angles. In the abscissa the angle of marking β is represented and in the ordinate the angle of entry of the sound γ is represented. While the polar diagram in the vicinity of the perpendicular direction (β = 0º) is symmetrical, the contour line 3dB similar to a banana with a target marked aft or forward is abolished. If the sound comes exclusively from the horizontal direction then the maximum of the polar diagram is always in the β coordinate exactly at the indicated target marking. However, if the sound also comes from a vertical direction, as indicated by way of example by the straight line drawn through the parallel with respect to the coordinate β then the maximum of the polar diagram along the line indicated in Figure 1 in a semicolon form of the maximum reception sensitivity towards greater horizontal β marking angles, which leads to a deviation from the true marking, that is, in general a marking angle β is marked Too big. The marking error generated in this case is symbolized in Figure 1 by the double arrow on the coordinate β. As the marking increases in size, that is, with the increasing marking angle, the deviation increases. As a consequence of this in the case of all linear and near-linear underwater antennas due to the large vertical opening angle 23dB of for example 75º (± 37.5º up and down) and in case of a vertical input of Sound systematic marking errors arise as a function of the β marking angle, as depicted in the diagram in Figure 2.

In a known procedure for determining depth values of the water profile from measured pulse travel times of emission pulses emitted by the transducer arrays and from the emission directions (DE 42 07 716 A1) to avoid errors due to at the specification of an incorrect sound velocity in the calculation of the depth values a correction factor is introduced with which the fixed sound velocity, measured on the surface of the water is multiplied to obtain the actual sound velocity in the measurement path For this, for each transducer array, depth values are determined in each case in the direction of the vertical plummet and for a perpendicular plummet direction with respect to the plane of the transducer array and by means of the depth values selected for all other directions. The estimated depth values of an estimation profile are determined from the plumb line. For at least one of the other plumb directions, the estimated depth value is compared with the depth value determined from the measured pulse travel time and from this the corrective factor for the set sound speed is determined.

The invention is based on the task of indicating a procedure for marking an objective of the type mentioned at the beginning that fails less and therefore produces more accurate markings.

This task is solved according to the invention by the features of claim 1.

The method according to the invention has the advantage that very large marking errors that occur especially in the case of marking angles that differ significantly from the perpendicular in the area called endfire of the underwater antenna are largely eliminated and with this results in reliable, equal markings in all the directions of marking of the linear underwater antenna. In the case of very high water depths in which the sound propagation model calculates a sound beam path that does not change in a range of angles around the measured target marking, a correction derived from the input angle is sufficient. of the vertical sound of the speed of sound that enters the time delay of the reception signals to obtain a very accurate marking also in the "endfire" zone by adjusting the polar diagram. In the case of reduced water depths in which the soil profile of the water channel can usually vary substantially in different marking directions and thus the propagation of the sound, an improved target marking is continuously obtained by iterative determination of the angle of vertical sound input and by repeated correction of the speed of the sound approaching towards a convergence value after a few iterations indicating the minimized marking in terms of errors towards the target.

Appropriate embodiments of the process according to the invention with advantageous developments and configurations of the invention result from the other claims.

According to an advantageous embodiment of the invention, the inverse value of the cosine of the input angle of the determined vertical sound is used as a correction factor for the multiplication with the speed of sound propagation.

The invention is described in more detail below with the help of an exemplary embodiment illustrated in the drawing. They show:

Figure 1 by way of example a contour line –3dB- of a polar diagram of an underwater antenna

linear lying across the marking or the marking angle β and the entry angle of

γ sound for three different dialing angles

Figure 2 a schematic representation of the linear antenna marking error as a function of β marking,

Figure 3 a functional diagram for the explanation of the dialing procedure,

Figure 4 a schematic representation of a sound ray path calculated using a model

Sound propagation within a vertical opening angle 2-3dB of the linear antenna for

a marking angle β = 45 °.

The procedure for marking a target that emits sound by means of an elongated underwater antenna is described in more detail below by means of the functional diagram depicted in Figure 3. With a lens that emits sound in this case it is understood a target away from the antenna that It generates sound, reflects sound and disperses backward sound that expands in the water and is received by the underwater antenna. Examples of an elongated or linear or linear-like underwater antenna are so-called towed antennas dragged by a boat (towed arrays) or a side antenna (flank array) arranged in the hull of the underwater vehicle boat or also PRS (passiv ranging sonar antennas) ) carried by a boat.

In the case of all antenna systems, the target marking is generally determined, that is, it is the marking angle that includes the probed direction towards the target with a reference direction, for example, the horizontal vertical with respect to the underwater antenna, from the output signals of the electroacoustic transducers by means of a target marking signal processing performed on a marking device. To do this, it is necessary to enter the current value of the sound velocity at the location of the underwater antenna that is generally measured earlier in the vicinity of the underwater antenna. The marking device is conceived differently from the underwater antenna used and in the case of using a linear antenna with a multitude of transducers placed in a row next to each other it is fundamentally different than in the case of the use of a so-called PRS antenna consisting of three electroacoustic transducer receiver bases arranged at a greater distance from each other that are arranged aligned with each other. Under the concept of linear antenna the aforementioned side antennas and towed antennas are subsumed.

In Fig. 3, a linear antenna 10 designed as a side antenna with a multitude of electroacoustic transducers 11 placed in a row next to each other is schematically represented. Generally the electroacoustic transducers 11 are arranged on an antenna support 12 at a constant distance d from each other. In the case of a lateral antenna normally each of the transducers 11, also called stave, arranged in a horizontal plane next to each other comprises several transducer elements arranged in a vertical plane, as it is not represented in more detail in this case. The number of vertical transducer elements, preferably placed equidistant from one another, is markedly smaller than the number of transducers 11 sharpened side by side horizontally for address generation. The output signals of the transducer elements arranged vertically one below the other are summed up and normalized and form the reception signals of the transducers 11 or staves, referred to below as reception signals. In the case of so-called towed antennas, the transducer elements arranged vertically one below the other are missing, so that here the output signals of the transducers 11 directly represent the reception signals. The marking device 17 connected to the outputs of the transducers 11 or staves comprises an address generator 18, also called a beam generator, a reception level meter 19 and a maximum level 20 detector. For target marking in the marking device 17 by means of a corresponding signal treatment with the reception signals of the electroacoustic transducers 11 or staves a fan 13 of direction functions or polar diagrams 14, also called a beam fan, is generated, where each polar diagram 14 (also called beam) has a small horizontal opening angle and a relatively large vertical opening angle that depends on the number of transducer elements arranged vertically one below the other of each transducer 11. The axes 15 of the polar diagrams 14 or of the beams represent the main direction of the polar diagram in which there is the maximum sensitivity d and reception. These are established and generated electronically by means of a horizontal turning angle or marking angle β in front of the common reference direction.

For the generation of the polar diagram 14 in the address generator 18, the reception signals of the transducers 11 or staves are temporarily delayed and in relation to the phase, and specifically in such a way that they are cofasic for a given reception or dialing direction βj. The delay times τi, j calculated according to

τi, j = i · d · without βj / ceinstell (1)

for this they are recorded in address generator 18 for all receiving addresses j (j = 1..m) and for all transducers 11 or staves i (j = 0..n). d is the horizontal distance between transducers on the antenna carrier 12 and ceinstell the speed value of the sound in the water entered in the address generator 18. The standard value for ceinstell is the cmess value of the sound velocity in place. of the antenna measured before the start of the marking process. The cofasic reception signals received in this case in each reception address are added to form so-called group signals. In the reception level meter 19, the levels of the group signals are measured and recorded by associating them with the reception addresses j or with the marking angles βj. A maximum level detector 20 determines the maximum of the level and emits the marking angle corresponding to the group signal with the maximum level as target marking βZk with k = 1, 2… K. This group signal with maximum level represents the polar diagram 14 in which there is a maximum of sound reception.

To substantially reduce the marking errors of the marking device 17 described at the beginning which are considerable especially for large β marking angles in block 21, the sound stripe path for a direction of sound is generated by a sound propagation model. Sound propagation that is predetermined by a received βZk target markup. Multiple models of sound propagation of this type are known. A list is found in this source: Heinz G. Urban “Handbuch der Wasserschalltechnik” STN ATLAS Elektronik GmbH, 2000, pages 305 and 306.

In Figure 4, the calculated path of the sound rays within a vertical opening angle of the linear antenna 10 of approximately 75 ° is shown schematically by way of a direction of sound propagation that is predetermined by an alleged marking of objective bZ1 = 45º as an example. Depth intervals are placed on the ordinate and distance intervals on the abscissa. The shaded area represents the bottom of the sea. From this sound ray path, the vertical γ sound input angle at the antenna site is determined for a distance towards the estimated target and a depth towards the estimated target.

In the representation in Figure 4 the antenna location is in proximity to the origin of the coordinate system. The distance to the target is either known or estimated with other sensors or procedures. For example, the distance to the target can be deduced from a procedure for passive determination of target data that is performed in parallel with the purpose of data support, as described for example in DE 101 29 726 A1. However, it can also be specified from previous objective markings. The diagram in Figure 4 assumes that the distance to the target mark of the target indicated with Z is 47kyd. Likewise, the depth of the objective is estimated, in this case, for example, 10m.

In the sound ray diagram, the sound beam that leaves the Z target that has the minimum damping is determined. In the example of Figure 4 among other things they expand two sound rays from the target located at a depth of 10m that reach the antenna site with a vertical sound input angle of 3.75º and 22.5º. The great damping of the sound propagation is done by reflections on the surface of the water and at the bottom of the sea. While the sound beam that leaves the Z target that reaches the antenna with a vertical input angle of 3.75º is exposed to a multitude of reflections on the water surface, for example the sound beam that comes out of the Z lens and that it reaches the antenna with a vertical entry angle of 22.5º due to the absence that background and surface reflection is only dampened by propagation losses in the water and therefore is essentially less damped. As vertical input angle, this input angle γk of 22.5 ° is therefore determined as the vertical sound input angle γ1 relevant to the target marking βZ1.

For the vertical sound input angle γK at the antenna site, obtained by a sound propagation model from the block 21 in the correction block 22 a correction factor is calculated as the inverse value of the input angle cosine γk vertical sound. With this correction factor, the measurement value of the cmess sound velocity used at the beginning of the marking for the generation of polar diagrams 14 or of the group signals is corrected. For this, the cmess sound speed is multiplied in the sound speed correction element 23 with the correction factor, according to

ceinstell = cmess · 1 / cos γk with k = 1, 2,… k

This new value of the sound velocity is now entered in the address generator 18. With the delay times τi, j of the set of stored delay times varied by this, a dialing is now performed again in the manner described above and obtained an improved βZk objective marking which in the previous example of a first objective marking βZ1 = 45 ° now leads to an improved objective marking of βZ2 = 41.3 °.

In the case of high water depths the bottom profile does not vary in a larger area around the direction of marking, so that the sound ray path calculated by the sound propagation model in block 21, as it is represented in Figure 4, its validity is maintained and also for improved βZ2 target marking and therefore generates the same vertical sound input angle of, for example, γ2 = 22.5 °. With this, the marking process can be completed and the improved βZ2 target marking determined by the marking device 17 is displayed and indicated as marking of the βZ target.

In shallow water areas with shallow water depth the background profile varies in different directions of sound propagation, so that for a new target marking in the sound propagation model, another sound beam and sound path is calculated. This results in a different vertical γk sound input angle. For the improved target marking obtained from βZ2 = 41.3 ° in the example the sound beam path newly calculated with the sound propagation model in block 21 for the same distance from the target and for the same depth of the target will result in Another angle of sound input γ2 vertical. Therefore the improved objective marking βZ2 of βZ2 = 41.3 ° in the example still contains a marking error although reduced. In order to also eliminate the improved βZk target marking (in the example βZ2 = 41.3 °), the same procedure is achieved as the objective marking βZ (k-1) obtained first (in the example βZ1 = 45 °). In block 21, the sound beam path for the Z target assumed at the same distance and at the same depth is calculated again using the sound propagation model for improved βZk target marking (in the example βZ2 = 41.3º ). From this sound beam path a new vertical γk sound input angle of for example γ3 = 33.75º is now determined and in the correction block 22 a new correction factor is calculated by calculating the inverse cosine value of This new vertical γk sound input angle. With the new sound input angle, in the example γ3 = 33.75 ° the new value of the ceinstell sound velocity to be introduced into the address generator 18 in the correction element 23 of the sound velocity is calculated again according to the formula (2). With the set of delay times modified in the address generator 18 due to the new ceinstell the target is probed again and a new improved marking results, for example, βZ3 = 37.84 °. This described process is repeated until the sound input angle γk determined from the sound propagation model obtained with the last improved βZk target marking and does not vary within predetermined limits. If this is the case, then the improved βZk target marking again and finally determined by the marking device 17 is displayed as the βZ target marking and is displayed. If in the example given last the vertical sound input angle γ3 = 33.75º no longer varies, then the target marking would be βZ = 37.84º.

The equality of the vertical sound input angles γk-1 and γk determined in two steps k followed with the sound propagation model in block 21 can be determined in a simple way such that the difference in the input angle is formed of γk vertical sound finally obtained with the improved βZk target marking again and the vertical γk-1 sound input angle obtained previously with the improved βZ (k-1) target marking. If this difference (γk -γk-1) is less than a set value S, then the equality and improved βZk target marking has been achieved, finally obtained as an output of the βZ target. For this, for example, the vertical γk-1 sound input angle previously obtained through a memory or a mobile register 23 is applied and the γk sound input angle subsequently obtained directly in the difference generator 24 and the difference a comparator 25 is compared with the set value S. If it falls below this set value S, then a door 26 is opened next to marking device 17, so that the newly improved target marking βZk, obtained finally it arrives at the display 27 and there it is visualized as marking of the βZ objective.

Claims (6)

1. Procedure for marking a target that emits sound by means of an elongated underwater antenna that has several electroacoustic transducers (11) in which a horizontal target marking (βZk) is determined selectively from the transducer reception signals as for the direction including a fixed value (cmess) of the sound velocity in the water measured especially at the antenna site, characterized by the following procedure step:  with a sound propagation model a sound ray path is calculated in a direction of sound propagation that coincides with a specific target marking (βZk),  a sound input angle (γk) at the antenna site is determined from the sound beam path for a distance to the estimated target and a depth to the estimated target,  a correction factor is deduced from the sound input angle (γk),  the value (cmess) of the set sound speed is corrected by multiplication with a correction factor and  with the corrected value of the sound velocity (ceinstell) an improved target marking (βZk) is determined again.

2.

Method according to claim 1, characterized in that with the improved target marking (βZk) the process steps are repeated iteratively until the vertical sound input angle (γk) determined in each case with the target marking (βZk) improved no longer changes and only changes little, and because the target mark (βZk) obtained last is issued as mark (βZ) towards the target.

3.

Method according to claim 1 or 2, characterized in that the inverse value of the vertical sound input angle cosine is calculated as the correction factor.

Four.

Method according to any one of claims 1 to 3, characterized in that the distance to the estimated target and the estimated target depth are determined from previous target markings or determined with other sensors and / or objective data determination procedures.

5.

Method according to any one of claims 1 to 4, characterized in that with the sound propagation model all sound rays entering a vertical reception sector of the underwater antenna (10) are calculated and for sound rays they are displayed the resulting vertical input angles and damping for each distance and depth interval, and because for the determination of the vertical sound input angle (γk) the input angle of that sound beam experiencing the lowest damping is determined from the target in distance and estimated depth.

6.

Method according to any one of claims 1 to 5, characterized in that for the determination of the target marking (βZk) of the reception signals of the transducers (11) a range of polar diagrams (14) having an angle of horizontal opening and a vertical opening angle and a main direction (15) of the maximum reception sensitivity rotated with respect to a common reference line (16) and the angle of rotation of the main direction (15) of that polar diagram ( 14) in which a maximum sound reception appears is displayed as target marking (βZk).

dialing error dialing error max. Comp.